A color image is printed on a web substrate (e.g., paper) by employing various methods, such as a flexographic printing method and a rotogravure printing method. The flexographic printing method is performed by employing a plate cylinder, an anylox roller and an impression roller. The plate cylinder is located between the anylox roller and the impression roller. The plate cylinder is in contact with the anylox roller and with the impression roller. The web substrate is wound around the impression roller. The plate cylinder includes a pattern of an image which is to be printed on the web substrate. The anylox roller picks up ink from an ink basin, as the anylox roller rotates, and the anylox roller transfers the ink to the plate cylinder. The plate cylinder forms the image on the web substrate, according to the pattern thereof. For printing a color image on the web substrate, a printing press includes a flexographic printing station respective of each color of a color gamut, located in sequence, for example, one flexographic printing station for producing the image in red, one for green, and one for blue. The outer surface of each of the rollers is made of a resilient material, such as rubber, so that the pressure there between can be adjusted, by varying the distance between the rollers.
Prior to the print run, the printing press has to be set up (i.e., adjusted) in order to print the image on the web substrate, at an acceptable quality level. Methods for setting up the printing press are known in the art. In a manual method, the operator runs the printing press, inspects the printed image, and adjusts the pressure between the rollers, until the printed image is acceptable. In an automatic method, an opto-electronic sensor senses an image of a printed contact strip on the web substrate, and a controller adjusts the pressure between the rollers, according to the width of the contact strip, and according to the output of the opto-electronic sensor. In another automatic method, the controller adjusts the pressure between the rollers, by comparing the contour of the current image, with that of a desired image which is stored in a memory.
U.S. Pat. No. 6,634,297 B2 issued to Poetter et al., and entitled “Device and Process for Setting the Printed Image in a Flexographic Press”, is directed to a system for setting up a printing job. The system includes a printing roller, an engraved roller, a counter-impression roller, an actuating device, a plurality of servo motors, a control and regulating unit, an input device and an input unit, and a camera. The control and regulating unit is connected to the input device, the input unit, the camera, and to the actuating device. The actuating device is connected to the servo motors. A first pair of servo motors is connected to each end of the engraved roller. A second pair of servo motors is connected to each end of the printing roller.
A paper web runs over the printing roller. The engraved roller is provided with an inking unit. The printing roller is provided with a plurality of blocks, to be printed on the paper web. The engraved roller picks up the ink from the inking unit, and transfers the ink to the printing roller by means of a contact there between. The printing roller transfers the ink to the paper web, by means of contact with the counter-impression roller, and in this manner, a pattern defined by the blocks of the printing roller, is printed on the paper web.
The first pair of servo motors provides horizontal movement of each end of the engraved roller. The second pair of servo motors provides horizontal movement of each end of the printing roller. The actuating device directs the servo motors to move each of the engraved roller and the printing roller, either individually or together, towards or away from the counter-impression roller. The desired contour which is to be printed on the paper web is entered into the control and regulating unit, by means of the input unit. The diameter of the printing roller and the thickness of the blocks are entered into the control and regulating unit, by means of the input device.
The camera scans the printed image and feeds the scanned image to the control and regulating unit. The control and regulating unit compares the scanned image with the desired contour, and directs the actuating device to control the servo motors, and to move the engraved roller and the printing roller to a position, which produces the qualitatively best printed image. The values respective of this position are stored in a storage of the control and regulating unit, so that the optimal setting can be found again.
U.S. Pat. No. 6,166,366 issued to Lewis et al., and entitled “System and Method for Monitoring and Controlling the Deposition of Patten and Overall Material Coatings”, is directed to a system for detecting voids in a cold seal. The system includes a computer processor, a printing cylinder, an anylox roller, an ink tank, a traversing mechanism, an encoder, a display monitor and a touch screen. The traversing mechanism includes a camera and a radiation source. The encoder is connected to the anylox roller. The computer processor is connected to the encoder, the camera, the radiation source, the display monitor and to the touch screen.
The anylox roller picks up the ink from the ink tank and transfers the ink to a printing plate of the printing cylinder, in order to form the cold seal on a web substrate. The traversing mechanism moves the camera and the radiation source across the entire width of the web substrate. The encoder provides the signal to the computer processor in order to trigger the radiation source.
To set up the system, an operator positions the camera over the web substrate, at a position of interest where the camera can automatically view the coating on the web substrate, via the touch screen, while viewing an image of the web substrate on the display monitor. When the camera is positioned at the position of interest, the operator stores the position of interest in the computer processor, as the coating defect analysis position. The operator enters the maximum allowable coating void warning size, via the touch screen, and enables the automatic void detection. The computer processor determines whether there is a void larger than the maximum allowable coating void warning size, by employing a coating defect detection algorithm. In case the computer processor detects such a void, the computer processor produces a warning beacon, and directs the display monitor to display the void.
U.S. Pat. No. 5,448,949 issued to Bucher and entitled “Method and Device for Adjusting a Contact Pressure Between Ink-Carrying Cylinders of a Printing Machine”, is directed to a system for setting up a printing job. The system includes a plate cylinder, a plurality of form rollers, a dampening roller, a connecting roller, a plurality of adjusting drives, a plurality of position sensors, an angular position sensor, two opto-electronic sensors and a control or regulating device. Each of the adjusting drives is connected to a respective one of the position sensors.
The form rollers and the dampening roller are connected with the respective adjusting drives. The angular position sensor is connected with a rotational axis of the plate cylinder. A flexible printing form is clamped to the plate cylinder. The position sensors, the angular position sensor, and the two opto-electronic sensors are connected to the control or regulating device.
The form rollers and the dampening roller are associated with the plate cylinder. The connecting roller is located between the form roller and the dampening roller. The two opto-electronic sensors are aimed at the surface of the flexible printing form, at the outer periphery of the plate cylinder, along a peripheral line. The adjusting drives provide engagement and disengagement of the form rollers and the dampening roller from the plate cylinder.
When the form rollers and the dampening roller are engaged with the plate cylinder, and when the plate cylinder is stationary, the form rollers and the dampening roller are inked, and a contact strip is formed on the surface of the printing form. When the plate cylinder rotates, the two opto-electronic sensors sense the contact strip. The control or regulating device determines the association between an output of the two opto-electronic sensors, and the form rollers and the dampening roller. The control or regulating device determines the width of the contact strip, according to outputs of the angular position sensor and the two opto-electronic sensors. The control or regulating device directs the adjusting drives to move the form roller and the dampening roller, according to the width of the contact strip, in order to adjust the contact pressure between each one of the form rollers and the dampening roller on one hand, and the plate cylinder on the other.
U.S. Pat. No. 5,841,955 issued to Wang and entitled “Control System For a Printing Press”, is directed to a system for adjusting various parameters of a printing press, in real-time, by comparing the variation of ink distribution for each of the cyan, magenta, yellow and black colors, in a current copy, with those in a reference copy. The system includes a digital computer, a first video camera, a second video camera, a pair of lights, and a support. The first video camera and the second video camera are connected with the digital computer. The first video camera detects attributes of ink from a sheet of paper, in the visible region of the electromagnetic spectrum. The second video camera detects attributes of the ink from the sheet of paper, in the infrared region of the electromagnetic spectrum.
The pair of lights is located above the support. The first video camera and the second video camera are located above the support, such that each of the first video camera and the second video camera can capture an image on the sheet of paper, which is placed on the support. The reference copy is placed on the support and each of the first video camera and the second video camera, captures a reference image respective of the reference copy. The digital computer stores the information respective of the reference image in a memory thereof. The current copy is placed on the support and each of the first video camera and the second video camera captures a current image respective of the current copy. The digital computer stores the information respective of the current image in the memory.
The digital computer converts the red, green, blue and infrared images captured by the first video camera and the second video camera, into four separated cyan, magenta, yellow, and black images, which represent the amount of ink present on the current copy, by employing an ink separation process. The digital computer performs the same ink separation process with respect to the reference copy. The digital computer detects the variation of ink distribution for each of the cyan, magenta, yellow and black inks, by comparing the current image with the reference image. The digital computer adjusts various ink parameters, such as ink feed rate and ink water balance, by analyzing the characteristic of the ink distribution variation.
UK Patent Application GB 2340075 A to Peer Dilling and entitled “Image-Data-Oriented Printing Machine and Method” is directed to a method for adjusting the printing parameters of a printing machine dynamically during the production run, and statistically prior to the production run. The printing machine includes an ink applicator roll, a plate cylinder, a transfer cylinder, an impression cylinder, a printing material, a plurality of actuators, a plurality of sensors, a doctor, and a computer.
The actuators and the sensors are connected to the computer. The doctor rests on the ink applicator roll. The ink applicator roll is in contact with the plate cylinder. The plate cylinder is in contact with the transfer cylinder. The transfer cylinder is in contact between the impression cylinder and the plate cylinder. The printing material passes between the transfer cylinder and the impression cylinder.
The computer includes an expert system. The ink applicator roll inks the plate cylinder which provides the printing material with an image, via the transfer cylinder. The sensors are of different types, such as rotational speed sensor, temperature sensor, layer thickness sensor, optical density sensor, and surface roughness sensor. The computer directs each actuator to vary the distance between the respective roller, according to a feedback from the respective sensor, and according to a quality strategy, such as homogeneity of the image, the contrast, the hue, the saturation, and the lightness of the image.